Patterns of species dominance, diversity and dispersion in ‘Khasi hill sal’ forest ecosystem in northeast India

Abstract

Background: The 'Khasi hill sal' forest ecosystem in Meghalaya, India represents the easternmost limit of sal distribution. We tested if tree diversity and compositional heterogeneity of this ecosystem was higher than other sal-dominated forests due to moister environment. Methods: Vegetation was sampled in 11 transects of 10 m width and up to 500 m length covering 5.2 ha area. All stems ≥ 10 cm girth at breast height were enumerated. Results: We found a pattern of mixed dominance of Shorea robusta (sal) and Schima wallichii and co-dominance of Pinus kesiya and Careya arborea. The Shannon's diversity index (H′) was 3.395 nats. This value is remarkably high and competitive to that of moist sal forests of eastern Himalayan foothills and sal-dominated forests of Tripura. A high value of H′ was manifested by: a) high species richness (S = 123), b) good equitability (70.6%), c) 'fair' resource apportionment, and d) abundance of rare species (84% species with less than one per cent of total individuals, 67% species with two or less individuals ha −1 and 59% species with one or less individuals ha −1 ). The compositional heterogeneity was 'fair' (Whittaker's β w = 3.15). The presence of Fagaceae with six species commanding 4.3% of importance value (IVI) and of a pine (P. kesiya) in sal forest was remarkable. As many as 58 species showed 'low density (≤ 10 individuals ha −1 ), uniform dispersion', five species achieved 'higher density (> 10 individuals ha

Rainforests north of the Tropic of Cancer: Physiognomy, floristics and diversity in ‘lowland rainforests’ of Meghalaya, India

“…These patterns substantiate the observations of Champion and Seth (1968) , and Whitmore (1984) that the dominance of trees over other growth forms is common in lowland forests in India. Notably, similar proportions of trees, shrubs and liana have been recorded in sal-dominated lowland forests in Darjeeling ( Shankar, 2001 ) and in Meghalaya ( Tripathi and Shankar, 2014 ). The dominance of phanerophytes in Meghalaya also conforms to findings in the equatorial rainforests of Malaya ( Poore, 1968 , Lee et al., 2002 ).…”

“…Champion and Seth (1968) further remarked that the natural regeneration of evergreen species was better in these forests than in dipterocarpus lowland evergreen rainforests in the Deomali Division of Assam. While forest types, such as the lowland ‘Khasi hill sal’ forests ( Tripathi and Shankar, 2014 ), montane evergreen rainforests ( Khiewtam and Ramakrishnan, 1993 , Jamir and Pandey, 2003 , Upadhaya et al., 2003 ) and subtropical pine forests ( Tripathi et al., 2003 ) have been extensively investigated, the floristics, structure and regeneration of the lowland rainforests of Meghalaya have yet to be studied.…”

Biodiversity Baseline Assessment:

“…The number of species recorded during the sampling of PwS forests (67) was lower than those reported by Tripathi and Shankar (2014) in India, though their sampling plots were considerably larger, and thus likely captured more forest variability and species. The comparatively small sample effort under the BBA also probably affected the SDI values, which were relatively low compared to SDI reported by Tripathi and Shankar (2014), which exceeded 3.3. However, mean PwS forest basal area was actually somewhat higher than that reported for sal-dominated forests in India (15.6 m 2 /ha).…”

“…Chilaune (Schima wallichii) and myna (Tertrameles nudiflora), each comprised 4.4% of the overall forest composition, though both were most prevalent in middle foothills sites (8.4% and 6.7% composition, respectively). Tripathi and Shankar (2014) noted similar overstory codominance between sal and other tree species, including chilaune in India, and regarded it as unusual since sal is typically solely dominant in forests in the region. In both PwS lower forest sites where it occurred, sal formed nearly pure overstories, comprising 78% of the tree composition.…”

Environmental Factors Influencing Tree Species Regeneration in Different Forest Stands Growing on a Limestone Hill in Phrae Province, Northern Thailand

“…The IVI value was calculated as the sum of the relative densities and relative basal areas of each species in each stand. We used this index to identify dominant species at each site (Koonkhunthod et al 2007;Juwarkar et al 2014;Tripathi and Shankar 2014). The seedling/sapling ratios of species with high IVI values were used as measures of regeneration among the dominant species in each forest stand.…”